Get the Gmail attachment filename without downloading it

问题

I'm trying to get all the messages from a Gmail account that may contain some large attachments (about 30MB). I just need the names, not the whole files. I found a piece of code to get a message and the attachment's name, but it downloads the file and then read its name:

import imaplib, email

#log in and select the inbox
mail = imaplib.IMAP4_SSL('imap.gmail.com')
mail.login('username', 'password')
mail.select('inbox')

#get uids of all messages
result, data = mail.uid('search', None, 'ALL') 
uids = data[0].split()

#read the lastest message
result, data = mail.uid('fetch', uids[-1], '(RFC822)')
m = email.message_from_string(data[0][1])

if m.get_content_maintype() == 'multipart': #multipart messages only
    for part in m.walk():
        #find the attachment part
        if part.get_content_maintype() == 'multipart': continue
        if part.get('Content-Disposition') is None: continue

        #save the attachment in the program directory
        filename = part.get_filename()
        fp = open(filename, 'wb')
        fp.write(part.get_payload(decode=True))
        fp.close()
        print '%s saved!' % filename

I have to do this once a minute, so I can't download hundreds of MB of data. I am a newbie into the web scripting, so could anyone help me? I don't actually need to use imaplib, any python lib will be ok for me.

Best regards

回答1:

Rather than fetch RFC822, which is the full content, you could specify BODYSTRUCTURE.

The resulting data structure from imaplib is pretty confusing, but you should be able to find the filename, content-type and sizes of each part of the message without downloading the entire thing.

回答2:

If you know something about the file name, you can use the X-GM-RAW gmail extensions for imap SEARCH command. These extensions let you use any gmail advanced search query to filter the messages. This way you can restrict the downloads to the matching messages, or exclude some messages you don't want.

mail.uid('search', None, 'X-GM-RAW', 
       'has:attachment filename:pdf in:inbox -label:parsed'))

The above search for messages with PDF attachments in INBOX not labeled "parsed".

Some pro tips:

label the messages you have already parsed, so you don't need to fetch them again (the -label:parsed filter in the above example)
always use the uid version instead of the standard sequential ids (you are already doing this)
unfortunately MIME is messy: there are a lot of clients that do weird (or plain wrong) things. You could try to download and parse only the headers, but is it worth the trouble?

[edit]

If you label a message after parsing it, you can skip the messages you have parsed already. This should be reasonable enough to monitor your class mailbox.

Perhaps you live in a corner of the world where internet bandwidth is more expensive than programmer time; in this case, you can fetch only the headers and look for "Content-disposition" == "attachment; filename=somefilename.ext".

回答3:

A FETCH of the RFC822 message data item is functionally equivalent to BODY[]. IMAP4 supports other message data items, listed in section 6.4.5 of RFC 3501.

Try requesting a different set of message data items to get just the information that you need. For example, you could try RFC822.HEADER or maybe BODY.PEEK[MIME].

回答4:

Old question, but just wanted to share the solution to this I came up with today. Searches for all emails with attachments and outputs the uid, sender, subject, and a formatted list of attachments. Edited relevant code to show how to format BODYSTRUCTURE:

    data   = mailobj.uid('fetch', mail_uid, '(BODYSTRUCTURE)')[1]
    struct = data[0].split()        
    list   = []                     #holds list of attachment filenames

    for j, k in enumerate(struct):
        if k == '("FILENAME"':
            count = 1
            val = struct[j + count]
            while val[-3] != '"':
                count += 1
                val += " " + struct[j + count]
            list.append(val[1:-3])
        elif k == '"FILENAME"':
            count = 1
            val = struct[j + count]
            while val[-1] != '"':
                count += 1
                val += " " + struct[j + count]
            list.append(val[1:-1])

I've also published it on GitHub.

来源：https://stackoverflow.com/questions/13663672/get-the-gmail-attachment-filename-without-downloading-it

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python

gmail

attachment

imaplib